Nikolas Cruz, the troubled 19-year-old suspected of killing 17 and injuring over a dozen in a shooting spree at Marjory Stoneman Douglas High School in Parkville, Florida, legally purchased the AR-15 rifle he allegedly used in the crime.

Sen. Bill Nelson of Florida said law enforcement officials had briefed him on Cruz, and that Cruz had undertaken "enormous preparation" for the shooting and was equipped with a gas mask and smoke grenades. Gas masks and smoke grenades are typically also legal for purchase with few restrictions around the US.

At 19 and without a criminal background and as a US citizen — despite Cruz's disciplinary record at school — all he needed was a few hundred dollars to buy the rifle.